Problem: Simplify the following expression: $a = \dfrac{3p}{4} - \dfrac{7p}{6}$
In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $6$ $\lcm(4, 6) = 12$ $ a = \dfrac{3}{3} \cdot \dfrac{3p}{4} - \dfrac{2}{2} \cdot \dfrac{7p}{6} $ $a = \dfrac{9p}{12} - \dfrac{14p}{12}$ $a = \dfrac{9p -14p}{12}$ $a = \dfrac{-5p}{12}$